1. Technical Field
The present invention relates to a sintering apparatus and a method for sintering for a porous glass base material.
2. Related Art
VAD, OVD and the like are known as a manufacturing method for an optical fiber glass base material. With these methods, at first, glass microparticles are generated by hydrolysis burning a glass raw material in a flame. Next, a porous glass base material is formed by attaching the generated glass microparticles to a rotating target rod. Further, the porous glass base material is sintered at 1400° C. to 1600° C., and a transparent optical fiber glass base material is obtained.
The porous glass base material is sintered at an atmosphere with a specific composition. During sintering in a sintering apparatus, if an outside air enters into a furnace core tube where the porous glass base material is housed, the quality of the manufactured transparent glass base material would be lowered. Also, if the atmosphere inside of the furnace core tube leaks to the outside, the environment would be contaminated. Here, there have been various structures proposed to close the furnace core tube in the sintering apparatus (for example, refer to Patent Document 1).